Classifications

• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
  • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
  • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
  • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
  • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
  • G06K19/073—Special arrangements for circuits, e.g. for protecting identification code in memory
• • G—PHYSICS
  • G07—CHECKING-DEVICES
  • G07F—COIN-FREED OR LIKE APPARATUS
  • G07F7/00—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus
  • G07F7/08—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus by coded identity card or credit card or other personal identification means
  • G07F7/10—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus by coded identity card or credit card or other personal identification means together with a coded signal, e.g. in the form of personal identification information, like personal identification number [PIN] or biometric data
  • G07F7/1008—Active credit-cards provided with means to personalise their use, e.g. with PIN-introduction/comparison system
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
  • G06Q20/00—Payment architectures, schemes or protocols
  • G06Q20/30—Payment architectures, schemes or protocols characterised by the use of specific devices or networks
  • G06Q20/34—Payment architectures, schemes or protocols characterised by the use of specific devices or networks using cards, e.g. integrated circuit [IC] cards or magnetic cards
  • G06Q20/341—Active cards, i.e. cards including their own processing means, e.g. including an IC or chip
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
  • G06Q20/00—Payment architectures, schemes or protocols
  • G06Q20/30—Payment architectures, schemes or protocols characterised by the use of specific devices or networks
  • G06Q20/34—Payment architectures, schemes or protocols characterised by the use of specific devices or networks using cards, e.g. integrated circuit [IC] cards or magnetic cards
  • G06Q20/357—Cards having a plurality of specified features
  • G06Q20/3576—Multiple memory zones on card

Definitions

• This invention relates to the filed of portable personal computers and more particularly to systems for maintaining data security in a portable digital information environment.
• the “Smart Card” has been used as a security tool.
• the “Smart Card” is a small microcomputer with writable, non-volatile memory and a simple input/output interface, fabricated as a single chip and embedded in a plastic "credit card”. It has exterior pins to allow it be connected to specially designed equipment.
• the program contained in the card's microcomputer interacts with this equipment and allows its non-volatile memory data to be read or modified according to a desired algorithm which may optionally include a password exchange. Special techniques have been implemented to protect the memory data and to allow permission variations according to the situation. For example, U.S. Patent No. 4,382,279 entitled, "Single Chip
• Microprocessor with On-Chip Modifiable Memory discloses an architecture which permits automatic programming of a non-volatile memory which is included on the same chip as a processing and control unit. As in other systems, the microprocessor only protects memory on the same chip.
• the "Smart Card” has been used both to facilitate the process of identification and to be the actual site of the valued information. In this situation, as in most prior situations, physical presence of a "key” as well as some special knowledge has been used as part of the verification or authentication process. In such cases, identification has involved a dialog between the person desiring access and a fixed agent such as a security guard and an automatic teller machine.
• flash memory combines the flexibility of random access memories (RAMs) with the permanence of disks.
• RAMs random access memories
• the above and other objects of the present invention are achieved in the preferred embodiment of a secure application card wich is operated in conjunction with one of more host systems such as the host system microprocessor described in a related patent application in the United States of America (Application nO 960 748) .
• the present invention extends the security for data to programs thereby providing a secure operating environment for running applications.
• the secure application card of the preferred embodiment includes a access control microprocessor (ACP) on a single semiconductor chip and one or more non volatile addressable memory chips which serve as main memory.
• ACP access control microprocessor
• the access control microprocessor chip and non-volatile memory chips connect in common to an internal bus having different portions for transmitting address, data and control information to such non-volatile memory chips.
• the access control microprocessor includes an addressable non-volatile memory for storing configuration information including a number of key values and program instruction information for controlling the transfer of address, data and control information on the internal bus.
• configuration information including a number of key values and program instruction information for controlling the transfer of address, data and control information on the internal bus.
• a portion of the configuration information serves as the content for the access by type memory which is loaded at power-up. This data is protected by the ACP and can be modified via the host processor only with proper permissions (via changing passwords) .
• the secure application card further includes an application microprocessor which also connects to the internal bus.
• the application processor as well as each of the other microprocessors which operatively connect to the card has an additional signal line included in the control portion of its bus interface carried through to the control portion of the internal bus which is used for indicating
• the access discrimination logic unit includes an access by type random access memory (RAM) having a plurality of word locations, each location associated with a different block of the addressable memory chips and having a number of access control bits coded for defining different types of access as a function of the specific application being run.
• RAM type random access memory
• Selector means within the access by type memory connects to the control portion of the internal bus and in response to signals applied to the "Execute" signal line and an "off board” signal line for designating whether the microprocessor source is located outside the application card (e.g.
• the selector means selects the bit location corresponding to the type of access requested and uses the bit contents of the designated access bit location to allow or disallow the transfer of an enabling control signal to the non-volatile memory chips.
• Off Board signal lines define several different types of memory access. These are: Data Read Access from the host microprocessor. Data Read access from the application card's microprocessor. Execute Access from the host microprocessor, and Execute Access from the application card's microprocessor.
• the access control microprocessor writes the contents of the access by type RAM in a conventional manner during power-up. As indicated, the host or application processor is allowed to modify the contents of this RAM only under the control of the ACP thereby maintaining security.
• each host microprocessor couples to the application card through a standard interface such as one of the interfaces which conforms to the Personal Computer Memory Card
• PCMCIA International Association
• XIP Execute-in-Place
• the present invention expands the capabilities of the secure memory card of the related patent application by providing security for programs thereby enabling application software to be packaged along with its required microprocessor in a self contained card that responds to cooperating/host microprocessor(s) over the standard shared bus by the use of well defined messages or protocols but shields its internal operation from such microprocessor(s) .
• This mode of operation conforms to the basic principal of object oriented software design whose goals are to provided a superior development environment by such segmentation of functions.
• the present invention achieves the same goals relative to providing a secure operating environment for applications.
• the present invention melds the "Smart Cart” and “memory card” technologies which is key to allowing the protection of large amounts of data made possible by flash memory technology in the "security harsh” environments created by electronic miniaturization.
• the present invention also retains the features of the secure card of the related patent application relative to being capable of operating in secure and non- secure modes, eliminating the need for encrypting and decrypting data, and protecting memory contents if the card or its host processor is lost, stolen, powered off or left unattended. In the event of theft, the memory contents is protected from access even if the memory card is opened and probed electronically or the memory chips are removed and placed in another device.
• Figure 1 is a block diagram of a system which incorporates an application card constructed according to the present invention.
• Figure 2 shows in greater detail, the flash memory of Figure 1.
• Figure 3 shows in greater detail, the access by type memory of Figure 1 constructed according to the teachings of the present invention.
• FIG. 4 is a system arrangement used to explain the operation of the application card of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT
• FIG. 1 is a block diagram of a secure portable hand-held computing system usable as a personal computer or as a transaction processor.
• System 1 includes an application card 3 constructed according to the present invention which connects to a host processor 5 by an external bus 102.
• the host processor 5 may take the form of a palm top personal computer, such as the HP 95LX manufactured by Hewlett-Packard Company.
• the host processor 5 includes a microprocessor 5-6 which connects to bus 102 via an internal bus 106 and the interface logic circuits of block 5-10.
• the host processor 5 also may include other units which connect to internal bus 106 such as a liquid crystal display (LCD) 5-2, a keyboard 5-
• LCD liquid crystal display
• keyboard 5- a keyboard
• the memory includes a one megabyte read only memory (ROM) and a 512 kilobyte random access memory
• RAM Random Access Memory Card
• the interface 102 provides a path for transferring address, control and data information between host processor 5 and the application card system 3 via a standard interface chip 104 and an internal bus 105.
• Each of the buses 102, 105, and 106 include a data bus, a control bus and an address bus and provide continuous signal paths through all like buses.
• bus 105 includes address bus 105a, data bus 105b, and control bus 105c.
• the application card 3 of the present invention includes an access control microprocessor (ACP) 10 which couples to bus 105, a plurality of CMOS flash memory chips designated as 103a through 103n which couple to internal bus 105, an application microprocessor Al which couples to bus 105 and an access discrimination logic unit* A3 which couples to bus 105 and to flash memories 103a through 103n as shown.
• ACP 10 is typically the same type of processing element as is used in the "Smart Card”.
• the CMOS flash memories 103a through 103n may take the form of flash memory chips manufactured by Intel Corporation. For example, they may take the form of the Intel flash memory chips designated as Intel 28F001BX 1M which includes eight 128Kilobyte x 8-bit CMOS flash memories.
• Intel 28F001BX 1M which includes eight 128Kilobyte x 8-bit CMOS flash memories.
• the access control microprocessor 10 and flash memories 103a through 103n can be constructed as disclosed in the above referenced related patent application .
• ACP 10 and non-volatile memory 103i will be briefly described herein.
• the control portion of internal bus 105 as well as external bus 102 contains a plurality of control signal lines which apply Execute, Read and Write control signals generated by any one of the microprocessors 5-6, 10 or Al. More specifically, each of the microprocessors include means for initiating Execute, Read and Write cycles of operation, through the different states of various control lines.
• the microprocessors may be constructed in a manner similar to Intel 486 DX microprocessors relative to including the capability of initiating code read, memory read and memory write bus cycles of operation by altering the states of specific control lines. For more information concerning such bus cycles, reference may be made to the publication entitled "Microprocessors Vol. I", Reference No. CG-110392 by Intel Corporation.
• the access discrimination logic unit A3 as discussed in greater detail in connection with Figure 3 includes an Access by Type Random Access Memory (RAM) array containing a plurality of word locations, one location for each block of the memory chips 103a through 103n and input selector circuits connected to the "Execute" and "Off Board” control signal lines indicating the nature and source of the memory access.
• these signals define four different types of memory access, These are: Data Read Access from Host Microprocessor 5-6, Data Read Access from the Application Microprocessor Al, Execute Access from the Host Microprocessor 5-6, and Execute Access from the Application Microprocessor Al.
• the Access Discrimination Logic Unit A3 performs the task of applying the output enable control to the memory chips 103a through 103n. That is, it determines which type of enable control signal is to be applied to the memory chips 103a through 103n as a function of the state of the selected prestored access control bits of the location associated with the block being addressed.
• the access control microprocessor (ACP) 10 of the preferred embodiment includes a protected non-volatile memory 10-2, a random access memory (RAM) 10-4, and an interval counter 10-6, all of which are diagrammatically represented in Figure 1.
• the non-volatile memory 10-2 dedicates a number of addressed lccations in which to store authentication information and programs. More sperifically, a group of memory locations store one or more personal identification numbers (PINs) , protocol sequences or other identification information for verifying that the user has access to • the system, and configuration information for identifying the blocks in flash memories 103a through 103n that the user may access in addition to a time interval value used for reauthentication. Additionally, another group of memory locations store information for a given application which is loadable into the access discrimination logic RAM for designating the type of accesses (i.e., is a map or image of the access by type RAM contents) .
• Another group of memory locations store the key values used for protecting each of the flash memories 103a through 103n or the codes used to protect the individual blocks of each of the flash memories 103a through 103n.
• a further group of memory locations store the program instruction sequences for performing the required authentication operations and for clearing the system if the preset conditions for failure are met.
• program instructions can be included to enable the user to control the setting of the interval counter 10-6 which establishes when user re ⁇ authentication takes place.
• FIG. 2 shows in block diagram form, flash memory 103a which is identical in construction to the remaining flash memories 103b through 103n. As shown, memory 103a includes two sections, a memory section 103M organized
• section 103M includes a memory array 54 organized into sixteen blocks as shown in Figure 4, a command register 50, input/output logic circuits 60, an address counter 56, a write state machine 61, an erase voltage system 62, an output multiplexer 53, a data register 55, an input buffer 51, an output buffer 52, and a status register 58, arranged as shown.
• the basic logic circuits of flash memory 103a take the form of the type of circuits included in flash memories manufactured by Intel Corporation. Since such circuits can be considered conventional in design, they will only be described to the extent necessary. For further information regarding such circuits, reference may be made to the publication entitled, "Memory Products", Order Number 210830, published by Intel Corporation, dated 1992.
• the flash memory circuits receive a plurality of input address signals A0-A16, data signals D00-D07 and control signals consisting of chip enable, write enable, output enable, power down and erase/program power supply signals CE, WE, OE, PWD, and VPP respectively.
• the CE, WE and OE signals are applied to command register 50 and I/O logic block 60 from host processor 5 via bus 102 and control bus 105b and dispersed to control the indicated logic blocks. More specifically, the output enable (OE) signal is applied as an input to output buffer 52 and in accordance with the present invention is provided by access discrimination logic A3 of Figure 1.
• the PWD signal is also applied to command register 50 for enabling the flash memory to perform other operations such as to clear the volatile storage elements of section 103S as desired thereby enforcing user reauthentication when normal operation is again resumed.
• section 103M operate in the following manner.
• Information is stored in memory array 54 via data bus 105a, input buffer 51 and data register 55 at an addressed location of one of the memory blocks specified by the address received by address counter 56 from address bus 105c.
• Information is read from a specified addressed location of a block of memory array 54 and is sent to host processor 5 via an output multiplexer 53, output buffer 52, data bus 105a and bus 102.
• a status register 58 is used for storing the status of the write state machine, the error suspend status, the erase status, the program status and the VPP status.
• the write state machine 61 controls the block erase and program algorithms.
• VPP voltage level
• section 103S includes a security access control unit 30 and a volatile access control memory 43 interconnected as shown.
• the output of the access control memory 43 is applied as an enabling input to output buffer 52 during each memory read cycle when the contents of a byte location of any block of memory array 53 is being read but. That is, a read cycle may occur, however, the data read out is inhibited from passing through output buffer 52 in the absence of the appropriate block's access control memory gating signal.
• access control memory 43 includes sixteen individually addressable bit storage elements, an input address 4 to 16 bit decoder connected to the input of each storage element and a 1 to 16 output multiplexer circuit connected to the output of each storage element. As shown, four bits of address latch counter 56 corresponding to the block address applied to control memory 43 are decoded and used to select the appropriate storage element output which is applied as an enabling input to output buffer 52.
• This section receives command control signals from command register 50 of section 103M.
• Special commands such as those described in the related patent application are added to the sets of commands used by the flash memory for implementing data security.
• the standard flash memory commands take the form of the commands utilized by the Intel Corporation flash memories.
• the application microprocessor Al is contained in the application card and is programmed to perform all operation f -unctions required for running a given application.
• the microprocessor may be constructed using an Intel 80286 microprocessor chip.
• the application microprocessor Al also has a random access memory which is uses to perform certain intermediate calculations in running specific applications.
• the application card 3 also operates in conjunction with the handheld point of sale host processor of Figure 4.
• This host processor includes a number of peripheral devices such as a display, keypad ticket printer, credit card reader and a communications link which connect in common to an internal bus.
• the host microprocessor is a simple device which operates the peripheral devices but has minimum functionality of its own.
• the microprocessor can be constructed using an Intel 8051 chip. It has its own read only memory (ROM) which contain start up and self test code only.
• ROM read only memory
• the host device can be viewed as an "shell" with all of the significant functionality contained within the application card 3.
• the access discrimination logic unit A3 as shown in
• Figure 3 includes a random access memory Bl having n groups of locations corresponding to the number of flash memories. Each group contains 16 multibit or word locations, one for each block contained in the flash memory 103a. The number of bit positions of each word correspond to the number of different types of accesses required for the application being run. For example, in the application card of the preferred embodiment, as discussed above, there are four different types of accesses. These accesses are designated by bit positions
• bit positions 0 and 1 are used to control application microprocessor access to data and programs respectively. Bit positions
• any bit position is preset to a binary ONE state, this indicates that access is permitted.
• a bit position is preset to a binary ZERO state, this indicates that access is not allowed.
• the RAM array Bl connects to the data bus portion 105b of internal bus 105 for loading by an authorized microprocessor. It also connects to the address portion 105a of internal bus 105 which supplies the most-significant bits of the memory address to act as an address to this array. The outputs of an addressed location are applied to the data inputs of a multiplexer
• the selector inputs of the multiplexer Bl connect to the "Execute” and “Off Board” control lines of the control portion 105c of the internal bus 105 as shown.
• the output of the multiplexer Bl is applied as one input to an AND gate B3 which has another input connected to the output enable control line of the control portion
• the AND gate B3 has its output connected to the output enable control line which is applied as an input to each of the memory chips 103a through 103n.
• the application card of the present invention will now be described relative to a particular application illustrated in the system configuration of Figure 4.
• the mainframe personal computer is used to all of the restaurant processing and can be constructed as the host personal computer 5 of Figure 1.
• the host personal computer 5 has, occupying a diskette slot, a device which accepts PCMCIA cards.
• Each application card can be plugged into that interface as well as into any one of the number of hand held devices, such as the device of Figure 4.
• each hand held device has a keypad, a small display and a credit card reader in addition to other required accessories.
• the data processing manager for the restaurant checks the group of hand held devices, one for every waiter, stored in a rack having their batteries recharged and without any cards. In another location, the manager locates a stack of application cards used the previous night. That is, the normal procedure is that when a waiter checks out, the waiter removes the card from the hand held device, places the device in the recharging rack and slips the card into a slot in a secure place in a door which can be only accessed by the manager.
• Each application card has the capability of recognizing two hosts which means that the access control microprocessor 10 of each card has been programmed to recognize two PINs.
• One is the PIN of the computer system which only the manager and the mainframe personal computer 5 knows.
• the other is the PIN assigned by each waiter at the beginning of every shift chosen from a list of generic PINs provided by the manager.
• the manager takes each application card and inserts it into the PCMCIA slot of the mainframe personal computer 5 which presents the higher level PIN.
• the most important information stored in each application card is a record of previous days transactions for a particular waiter for a given shift. This provides an audit trail which eliminates the need to process large amounts of paper receipts.
• AD « application data
• AP application program
• HD host data
• HP host program
• the daily transaction history data is shown as data which is accessible only to the application microprocessor Al in the hand held device and not the hand held device itself for the reasons discussed herein.
• An area of memory 103a corresponding to two blocks hap been allocated for storing this information.
• the first bits of each of the words W14 and W15 associated with the allocated blocks are set to binary ONES for designating read access only by the application microprocessor Al.
• the transaction history data will later be made accessible to the mainframe personal computer 5 under the control of ACP10. While the hand held device is in the hands of the waiter, a closed transaction is stored within the application card and is accessible only to the application microprocessor Al on the card. This prevents tampering with such data by any one.
• the application card When the application card is placed into the mainframe personal computer 5, it now presents a PIN or password which is used by ACP10 to verify that the host computer 5 has the correct permissions. Only when the appropriate permissions have been presented does ACP10 modify the content of the RAM array to provide the appropriate access (i.e., sets the third bits of each of the words W14 and W15 are set to binary ONES.
• the access discrimination logic volatile RAM array When the access discrimination logic volatile RAM array is reloaded, the mainframe computer 5 is now allowed to read this data which in the hand held device was unavailable to it.
• the volatile RAM memory of the access discrimination logic A3 is set up by ACP10 so that the mainframe computer 5 has free access to all of the application card's information. The setup is under the control of the ACP for maintaining security.
• the first thing the manager does is capture all of the previous night's transactions and stores them in the mainframe computer 5 for later processing as appropriate
• mainframe computer 5 when the mainframe computer 5 provides the correct PIN, it can cause the ACP 10 to set up the RAM B3 of the access discrimination logic A3 and the locks within the flash memories 103a through 103n to allow the mainframe computer 5 to read all of the data stored in such memories. After the data has been stored, those memory blocks are cleared/erased and rewritten for later use.
• Another type of information stored in memory 103a of the application card is the drivers for the devices on the hand held device.
• the area of memory corresponding to 5 blocks has been allocated to the storage of this information.
• the blocks have associated therewith, words WO through W4, each of which has bit position 4 set to a binary ONE state for designating access only by the hand held host of Figure 4.
• the update would be written into the flash memory at this time by the manager.
• the mainframe host processor 5 identify itself wherein different hosts can have different levels of privilege, the entire application card whose memory had been cleared can be updated so as to be ready for the next day's use and may be personalized for specific people on the service staff or the same information may be written into all of the cards.
• the programmed application cards are placed in a stack and when an individual comes in to start work, that individual will take a hand held device from the charging rack and select a personalized card if so specified (e.g. bartenders -one type, waiters another type) which will be inserted into the handheld device.
• a personalized card e.g. bartenders -one type, waiters another type
• the individual will insert a generic PIN requiring the individual to identify themselves as the user which allows the person to select a PIN to use for that person' ⁇ shift for added security.
• the mainframe computer 5 would be able to obtain the data through the use of its overriding PIN.
• all of the application card data would be protected from being improperly accessed through the security unit of the application card as described in the cited related patent application . That is, access could only be gained through the use of a master PIN which is only known by the mainframe computer 5.
• This security allows the restaurant to operate without paper slips. Therefore, there is no need to maintain carbon copies thereby ensuring protection of customer credit card data.
• the printer in the hand held device would be used to print a single copy of a receipt for each customer who requests such a receipt. If the hand held device had a pen surface on it, this could also capture the customer's signature.
• the four areas of memory will have been properly setup pursuant to the table and the hand held device is now in the hands of the service personnel.
• the data area is reserved to the applications microprocessor A3 for storing closed transactions for the day which will be in a protected area (i.e., controlled by the coding of words W14 and W15) for both security reasons and so that they are properly preserved (e.g. not overridden by accident) .
• This is an advantage of flash memory in that it eliminates the need for special battery backup circuits to preserve such information.
• the hand held host processor would not have access to this type of information for purposes of robustness. If there were bugs or errors in the code that branched off into the wrong area, it would be trapped out and not permitted access to such code.
• the program code of the hand held host processor similarly is protected from access by the application microprocessor Al for the purposes of robustness. Also, it allows the hand held device to be programmed more simply and reduces the amount of memory required. Thus, the present invention, by allowing two microprocessors to share memory, results in a more economical system implementation.
• the hand held host processor and application processor Al of Figure 4 generate memory addresses as required for accessing flash memory 103a.
• the most significant bits of the memory address are applied to the address inputs of RAM Bl of Figure 4 via the address bus 105a. This causes the read out of the multibit contents of the designated word location.
• the states of the "Execute” and “Off Board” lines applied as inputs to multiplexer B2 select the appropriate bit location. The state of this bit in turn controls output AND gate B3 to allow or disallow the transfer of the signal applied to the Output Enable control line to memory section 103m of Figure 2. That is, read access is allowed or disallowed by preventing the output buffer 52 from applying the information read out from memory 54 to the data portion 105b of internal bus 105.
• the application card constructed according to the principles of the present invention provides a secure environment for both data and programs. It allows sharing of such information stored within a non-volatile memory between a plurality of microprocessors. Further, it enables application software to be packaged with its own application processor making such systems more economical to produce and use.

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• 1994
  • 1994-01-14 US US08/181,684 patent/US5491827A/en not_active Expired - Lifetime
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